Use of coating compositions for wind turbine blades

ABSTRACT

The present invention relates to coating compositions for wind turbine blades. The compositions are particularly useful as topcoats for wind blades and for Leading Edge Protection (LEP). The invention also relates to a wind blade coated with a coating composition of the invention and to a method for application of the coating composition and to a method for repairing and/or replacing the existing coating layer on a wind blade by application of a coating composition of the invention. The invention also relates to a kit of parts comprising the base composition and the curing agent used in the coating composition. The coating composition used for coating a wind blade comprises a base composition comprising a polyetheraspartic ester having the formula (I) below, wherein each R represents a linear or branched C 1 -C 10  alkyl residue, such as a linear or branched C 1 -C 6  alkyl residue, such as for example a methyl, ethyl, propyl or butyl residue; and wherein X is a polyether. The coating composition further comprises a curing agent.

FIELD OF THE INVENTION

The present invention relates to coating compositions for wind turbineblades. The compositions are particularly useful either as topcoatcompositions or as compositions for Leading Edge Protection (LEP). Theinvention also relates to a wind blade, such as the leading edge of awind blade coated with coating compositions of the invention and to amethod for application of the coating composition and to a method forrepairing and/or replacing the existing coating layer on a wind blade byapplication of a coating composition of the invention. The inventionalso relates to a kit of parts comprising the base composition and thecuring agent used in the coating compositions.

BACKGROUND OF THE INVENTION

In recent years, wind energy has become an important source ofelectricity production, and contributes significantly to reducing CO₂emissions. Wind power is the use of air flow through wind turbines toprovide the mechanical power to turn electric generators.

Wind turbines typically have an upwind rotor with three blades, attachedto a nacelle on top of a tall tubular tower. Wind turbine blades, or“wind blades” are usually designed to last around 20 to 25 years. Theblades are constantly exposed to the elements and are ideally designedto endure temperature extremes, wind shears, precipitation, and/or otherenvironmental hazards with minimal failure. Coating failure due toerosion is often observed on the leading edge of the blade. Rain, hail,ice, UV, water absorption and other weather conditions erode the leadingedge of the blade. This affects the aerodynamic of the blade and couldcause severe damages.

Common concepts for protecting the leading edge of wind turbine bladesare for example application of an anti-erosive tape or application of asuitable coating composition (see e.g. Herring, Dyer, Martin and Ward.Renewable and Sustainable Energy reviews 115 (2019) 109382). For bothconcepts good adhesion to the blade and good resilience properties areof outmost importance. For coating compositions the material propertiesalso plays a significant role in order to obtain the right balancebetween e.g. robustness, hardness and elasticity of the coating.Furthermore, it is desirable that the coating compositions can be easilyapplied to the wind blade.

Various types of coating compositions are used in protective coatings ofwind blades for minimizing erosion including compositions formed fromaliphatic polyaspartic esters and isocyanate curing agents. For exampleWO 2015/136018 suggests the use of aliphatic polyaspartic esters informulations for wind blade coating and WO 2015/049260 discloses coatingcompositions comprising an aliphatic polyaspartic ester and apolyisocyanate curing agent and further comprising solid particles of anamino resin based polymer. WO 2015/120941 discloses coating compositionscomprising aliphatic polyaspartic esters and at least one polycarbonatediol in the paint base.

SUMMARY OF THE INVENTION

The present invention provides new coating compositions for wind turbineblades. Within the scope of the invention are coating compositions thatare useful for Leading Edge Protection (LEP) and compositions that areuseful as topcoat compositions for wind turbine blades.

Accordingly, in one embodiment the present invention relates to the useof a coating composition comprising

-   -   a) a base composition comprising a polyetheraspartic ester        having the formula (I) below

-   -   -   wherein each R represents a linear or branched C₁-C₁₀ alkyl            residue, such as a linear or branched C₁-C₆ alkyl residue,            such as for example a methyl, ethyl, propyl or butyl            residue; and wherein X is a polyether;            and

    -   b) a curing agent;        for coating a wind turbine blade.

In one embodiment, the invention relates to a wind turbine blade havingon at least a part of the outer surface thereof, a coating made from acoating composition as described above.

Definitions

In the context of the invention, the “leading edge” of a wind bladeindicates the portion of the blade that first cuts into the wind. Theopposite edge can be denoted “the trailing edge”.

The term “Leading Edge Protection” is typically abbreviated “LEP”. Inthe present context the terms “Leading Edge Protective coating(composition)” or “LEP composition” are used interchangeably andindicate a coating composition applied to at least a part of a windblade including at least to the leading edge or at least to a part ofthe leading edge of a wind blade to provide protection against erosioncaused by for example rain, hail, ice, UV, water absorption and otherweather conditions. One way to assess the effectiveness of a LeadingEdge Protective Coating is the Rain Erosion Test (RET) described in theexperimental section herein. Preferably said LEP is applied on top of atopcoat, but can also be applied under the topcoat, then preferably ontop of a primer layer.

In the present context, the term “topcoat” refers to a coating layerapplied to at least a part of a wind blade, preferably to the entirewind blade. Preferably, said topcoat coating composition (or “topcoatcomposition” is applied on top of a primer layer. Various primercompositions for wind blades are known in the art.

In the present context, the term “outermost layer” refers to the finalcoating system applied to the wind turbine blade, i.e. the outermostlayer when the wind turbine blade is in operation. The “outermost layer”of the leading edge is typically a coating made from a LEP coatingcomposition while the outermost layer of other parts of the wind bladetypically refers to a coating made from a topcoat composition.

In terms of the complete coating composition, it typically consists of a“base composition” (In which the base component is included) and a“curing agent” (in which the curing agent component is included).Typically the coating composition further include a number of otherconstituents, e.g. filers and pigments, additives and solvents. Itshould be understood that when reference is made to the “coatingcomposition”, it is the mixed composition, comprising both the basecomposition and the curing agent, ready to be applied to the wind blade.

In the present context a “blend of polyetheraspartic esters” or “apolyetheraspartic ester blend” indicates a blend of at least twodifferent polyetheraspartic esters.

In the present context, a “kit of parts” concerns a kit of partscomprising two or more containers, wherein one container comprises thebase composition and another container comprises the curing agent. Theother constituents that might be present in the coating composition ofthe invention as defined herein e.g. fillers, pigments, solvents andadditives, may be contained in either of the two containers of the kitof parts, typically in the container comprising said base composition.Alternatively, said other constituents may be contained in one or morefurther containers.

The term “polyether” indicates a polymer prepared by joining together orpolymerizing many molecules of simpler compounds (monomers) byestablishing ether links between them. In the context of the presentinvention, the term “polyether” preferably indicates a polymer in whichthe repeating unit contains an alkyl residue of one or more carbon atomslinked by an oxygen atom, such as an alkyl residue of between two to sixcarbon atoms linked by an oxygen atom, such as an alkyl residue of twocarbon atoms linked by an oxygen atom. One or more of said carbon atomsmay be substituted with a small alkyl such as for example methyl, ethylor propyl; preferably methyl.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to new coating compositions for windturbine blades, wherein the base composition comprises apolyetheraspartic ester having the formula (I) below

wherein each R represents a linear or branched C₁-C₁₀ alkyl residue,such as a linear or branched C₁-C₆ alkyl residue, such as for example amethyl, ethyl, propyl or butyl residue; and wherein X is a polyether.The coating composition also comprises a curing agent.

Polyetheraspartic esters are distinguished from the more conventionalaliphatic polyaspartic esters in that X in an aliphatic polyasparticester typically is an aliphatic straight or branched alkyl and/orcycloalkyl residue instead of a polyether.

In one embodiment, the invention relates to coating compositionscomprising a blend of polyetheraspartic esters wherein X is a polyetherhaving a repeat unit of the structure:

wherein m is in the range of 2 to 35.

The blend of polyetheraspartic esters may comprise at least twodifferent polyetheraspartic esters which have a different number ofrepeating units in X. In one embodiment, the blend is such that theaverage value of m is in the range of 2 to 10, such as 2 to 6, such as 2to 4, such as 2.5 to 3.

Polyetheraspartic esters may be prepared by reacting one or morepolyether polyamines with a dialkylmaleate, such as for example a linearor branched C₁-C₁₀ dialkyl maleate, such a linear or branched C₁-C₆dialkyl maleate, such as for example diethyl maleate. Saidpolyetheraspartic esters may be prepared, for example, by employing thereactants in amounts such that there is at least one equivalent, and insome embodiments approximately one equivalent, of olefinic double bondsfor each equivalent of primary amino groups. Examples of methods for thepreparation of polyetheraspartic esters can be found in WO 2014/151307and in Chen et al., RSC Advances (2018), 8: 13474-13481.

Suitable polyether polyamines that may be reacted with dialkylmaleatesin Michael addition reactions to produce polyetheraspartic esters forthe coating compositions of the invention include the JEFFAMINEpolyetheramines commercially available from Huntsman Corporation, TheWoodlands, TX; for example polyetheramines from the Jeffamine D series,such as for example Jeffamine D-230. In one embodiment, the blend ofpolyether polyamines comprises a blend of polyether polyamines accordingto formula (II) below, wherein p is a number having an average value ofat least 2, such as 2 to 35, or 2 to 8, or 2.5 to 6.1

wherein the blend comprises: (1) about 50 to 99% by weight, such as 50to 90% by weight, or, in some cases, 80 to 90% by weight, of polyetherpolyamines according to the formula wherein p has an average value of2.5; and (2) about 1 to 50% by weight, such as 10 to 50% by weight, or,in some cases, 10 to 20% by weight, of polyether polyamines according tothe formula wherein p has an average value of 6.1.

An example of a blend of polyetheraspartic esters that is suitable foruse in the present invention is Desmophen NH 2850 XP, from CovestroDeutschland AG, Leverkusen, Germany, which has an equivalent weight ofabout 295, a viscosity at 25° C. of about 170-210 mPa·s, and an aminevalue between 170-210 mg KOH/g.

The use of polyetheraspartic esters in coating compositions are knownfrom WO 2014/151307 which discloses a coating composition with a resincomprising a polyetheraspartic ester in combination with an aliphaticpolyaspartic ester made with Jeffamines. WO 2014/151307 specificallydiscloses a polyetheraspartic ester made with an aliphatic trifunctionalpolyether polyamine. WO 2014/151307 does not disclose or suggest the useof polyetheraspartic esters in coating compositions for wind bladesneither does WO 2014/151307 suggest using a difunctionalpolyetheraspartic ester.

Polyetheraspartic ester blends have furthermore been suggested for usein sealant compositions in WO 2016/049104 wherein polyetherasparticester blends are used in combination with an aliphatic polyasparticester and/or polyether diol. Said sealant compositions are intended forapplication at for example, expansion joints, control joints, andperimeter joints, of substrates, such as concrete substrates.

Polyetheraspartic ester blends have furthermore been suggested forexample for use in peelable automobile coatings (EP3495403) and for usein floor and countertop coatings in combination with anacrylate-containing compound (US 2018/0362801).

In one aspect, the coating composition of the present inventioncomprising one or more polyetheraspartic esters is a LEP coatingcomposition for wind blades. Said LEP coating provides good protectionagainst erosion which has been demonstrated by the Rain Erosion Test.The LEP composition is capable of providing protection in theparticularly harsh rain erosion conditions experienced by wind turbineblades.

In another aspect, the coating composition of the present invention isfor a topcoat coating composition for wind turbine blades. Both thetopcoat composition and the LEP composition possess good mechanical andphysical properties including a high degree of flexibility, which canfor example be assessed by the conical mandrel or tensile stress assays.Furthermore, both the topcoat and the LEP coat provides protectionagainst rain erosion.

The compositions of the invention can be applied using standardtechniques such as by brush and roller and can even be applied by sprayapplication, such as by conventional air-atomized spray application(topcoat composition) or by airless spray application (both topcoat andLEP compositions). The suitability for spray application is an advantageboth in relation to initial coating of a wind blade and in relation torepairing and/or replacing or partly replacing the existing coatinglayer on a wind blade.

The coating compositions of the invention may also comprise certainamounts of one or more aliphatic polyaspartic esters, which is anoptional ingredient when the composition is for use as a LEP coatingcomposition. Aliphatic polyaspartic esters are well known in the art.For a typical aliphatic polyaspartic ester X as illustrated in formula(I) is a straight or branched alkyl and/or cycloalkyl residue. Typicalexamples of aliphatic polyaspartic esters include substances sold underthe trade names Desmophen NH 1220, Desmophen NH 1420, Desmophen NH 1423,Desmophen 1520 and Desmophen NH 1521 commercially available fromCovestro Deutschland AG, Leverkusen, Germany.

If the coating composition is for use as a topcoat, the compositioncomprises one or more aliphatic polyaspartic esters in addition to thepolyetheraspartic ester blend. The ratio of polyetheraspartic esterblend to aliphatic polyaspartic esters is typically in the range of40:60 to 60:40, such as in the range of 45:55 to 55:45, such as about50:50.

Preferably, if the coating composition is for use in Leading EdgeProtection and comprises one or more aliphatic polyaspartic esters, theratio of polyetheraspartic ester blend to aliphatic polyaspartic estersis in the range of 70:30 to 99:1, such as in the range of 80:20 to 99:1,such as in the range of 85:15 to 99:1, most preferably in range of 90:10to 99:1 such as 95:5 to 99:1. In a preferred embodiment, the basecomposition comprises less than 20%, such as less than 15%, such as lessthan 10%, such as less than 5%, such as less than 1% of any aliphaticpolyaspartic esters by weight of said base composition. In oneembodiment, said LEP composition is substantially free of any aliphaticpolyaspartic esters.

Curing Agent

The coating composition of the invention further comprises a curingagent. In a preferred embodiment, said curing agent comprises one ormore polyisocyanates. In the present context, “polyisocyanate” refers toany organic compound that has two or more reactive isocyanate (—NCO)groups in a single molecule such as diisocyanates, triisocyanates,tetraisocyanates, etc., and mixtures thereof. Cyclic and/or linearpolyisocyanate molecules may usefully be employed. The number ofisocyanate groups per molecule is readily determinable via theisocyanate content and the number-average molecular weight of therespective polyisocyanate. The isocyanate content can be determined forexample in accordance with DIN EN ISO 11909 by reaction of therespective sample with excess dibutylamine and back-titration of theexcess with hydrochloric acid against bromophenol blue.

Examles of polyisocyanates according to the invention are compounds thatare known per se, preferably aliphatic polyisocyanates with particularmention of diisocyanates and their dimers and trimers such as uretdionesand isocyanurates. Examples include derivatives ofhexamethylene-1,6-diisocyanate (also denoted hexamethylene diisocyanateor HDI), octamethylene diisocyanate, decamethylene diisocyanate,dodecamethylene diisocyanate, tetradecamethylene diisocyanate,trimethylhexane diisocyanate, tetramethyl-hexane diisocyanate,isophorone diisocyanate (IPDI), 2-isocyanatopropylcyclohexyl isocyanate,dicyclohexylmethane 2,4′-diisocyanate, dicyclohexylmethane4,4′-diisocyanate, 1,4- or 1,3-bis(isocyanato-methyl)cyclohexane, 1,4-or 1,3- or 1,2-diisocyanato-cyclohexane, and 2,4- or2,6-diisocyanato-1-methyl-cyclohexane, and mixtures of these. Mostpreferred is hexamethylene diisocyanate (HDI).

Also, reaction products or prepolymers of aliphatic polyisocyanates maybe utilized. Particular mention is made of biurets, allophohanates,uretdiones and isocyanurates of the stated polyisocyanates. Preferencehere is given to using the dimers and/or trimers of the statedpolyisocyanates, preferably of hexamethylene diisocyanate. Inparticular, the uretdiones and isocyanurates of the abovementionedpolyisocyanates, that are known per se and also available commercially.

Isocyanurates can be prepared from any of a very wide variety ofisocyanates, in the presence of particular catalysts, examples beingsodium formate, potassium acetate, tertiary amines, ortriphenyl-phosphines. The isocyanurate ring system constitutes a trimerconsisting of three isocyanate groups in each case, are very stable,retaining their integrity even at high temperatures of more than 100°C., for example. Each of these three isocyanate groups originates fromthree different molecules of the respective isocyanate used; in otherwords trimeric structures are formed.

If polyisocyanates are used, examples being diisocyanates such as HDI,it is possible for an intermediate crosslinking to occur, and hence aplurality of isocyanurate rings may become linked to one another. It isknown also to be possible for fractions of bridging diols, as forexample hexanediol, to be added during the preparation of theisocyanurates, in order to modify their reactivity, for example, and inthis way for a plurality of isocyanurate ring systems to become joinedto one another. Likewise uretdiones, consisting of two isocyanate groupscan be prepared by a similar catalytic reaction.

In one embodiment, said curing agent comprises a prepolymer based on analiphatic polyisocyanate, preferably hexamethylene diisocyanate.“Prepolymers” in the context of the invention, are NCO-functionalreaction products of isocyanates and polyols, such as polyethers orpolyesters.

An exemplary prepolymer is a polyisocyanate containing aliphaticpolyester groups which comprises repeating structural units—R—C(═O)—O—C—, where R is a divalent aliphatic radical. Preferredaliphatic polyester groups are polylactone groups, more particularlypolycapro-lactone groups. Polycaprolactones and their preparation, byreaction of a monoalcohol with epsilon-caprolactone, for example, areknown. They may be introduced, for example, by common methods, viareaction of an isocyanate group with at least one of the hydroxyl groupsthey contain. As a result of the polyester groups present and of theintermediate crosslinking, where it occurs, polyisocyanates such as forexample hexamethylene diisocyanate (HDI) isocyanurates containingaliphatic polyester groups have a lower isocyanate content than, a pureHDI trimer. While the latter has an isocyanate content of about 25%(molecular weight 3×NCO=126 g/mol; molecular weight of the purelytrimeric isocyanurate of HDI=504.6 g/mol), the polyisocyanate containingaliphatic ester groups typically possesses an isocyanate content of5-20%, such as 5-15%, preferably 6-14%, such as 6-11% or 8-14% or10-12%, such as about 11%. A commercially available polyisocyanateprepolymer containing aliphatic polyester groups is Desmodur E 2863.Another exemplary prepolymer based on HDI is Desmodur XP 2599 containingether groups. Both prepolymers mentioned above are available fromCovestro Deutschland AG, Leverkusen, Germany.

Preferred polyisocyanates are solvent-free and are substantially free ofisocyanate monomer, i.e. contains less than 0.5% and more preferablyless than 0.3% of isocyanate monomer as measured according to DIN EN ISO10 283.

When polyisocyanates are used as curing agents, the functionality isdefined as the number of isocyanate groups present per molecule. Forpractical purposes, the number of isocyanate groups is provided as anaverage due to the presence of various related types of polyisocyanatemolecules within a commercial product. The expression “averagefunctionality” refers to the functionality of a combination of two ormore polyisocyanates. The “average functionality” is calculated as thetotal number of reactive (isocyanate groups) divided by the total numberof polyisocyanate molecules. Typically, lower functionality yields lesscrosslinking, which results in more flexible, softer products, andhigher functionality yields higher crosslinking and resulting stiffer,harder products. In a preferred embodiment, the average functionality ofthe polyisocyanates used in the composition of the present invention isin the range of 2-4, such as in the range of 3-4 or 2-3, such as in therange of 2-2.5.

Examples of commercially available polyisocyanates which are usefulwithin the present invention include Desmodur N 3900, Desmodur E 2863XP, Desmodur N 3800, Desmodur XP 2860 and Desmodur XP 2599; allavailable from Covestro Deutschland AG, Leverkusen, Germany. In oneembodiment, the curing agent according to the present invention compriseone or more polyisocyanates selected from the group consisting ofDesmodur N 3900, Desmodur E 2863 XP, Desmodur N 3800, Desmodur XP 2860and Desmodur XP 2599.

The choice of the one or more polyisocyanates to be comprised in thecuring agent may be based on the desired properties of the coatingcomposition, such as the preferred degree of viscosity of the coatingcomposition and flexibility of the coating layer. The term “one or morepolyisocyanates” indicates that a blend of polyisocyanates can be used.

For both the topcoat and the LEP composition of the present invention,the total number of isocyanate groups in the curing agent component tothe number of amine groups in the base component will typically be inthe range of 80:100 to 160:100, such as 90:100 to 125:100, such as95:100 to 120:100, preferably in the range of 100:100 to 120:100, suchas 100:100 to 110:100 or 105:100 to 110:100. Preferably, the number ofisocyanate groups is in excess of the number of amino groups, preferablyjust in minor excess in order to facilitate complete reaction of theamine groups.

Preparation of the Coating Compositions of the Invention

The coating compositions can be prepared from commercially availablecomponents. The base composition (including the one or morepolyetheraspartic esters and potentially one or more aliphaticpolyaspartic esters) and the curing agent (including the one or morepolyisocyanates) may typically also comprise one or more otherconstituents, e.g. fillers and pigments, solvents and additives (e.g.thickening agents, wetting agents, dispersing agents, anti-sag agents,anti-settling agents, defoamers, and stabilizers).

Examples of fillers and pigments are calcium carbonate, dolomite, talc,mica, barium sulfate, kaolin, silica, titanium dioxide, red iron oxide,yellow iron oxide, black iron oxide, carbon black, phthalocyanine blueand phthalocyanine green. In the LEP coating composition the totalamount of filler(s) and pigment(s) is preferably between 5-30%, such asbetween 10-25% by weight of the coating composition while the topcoatcoating composition preferably contains about 20-40% such as about25-30% of filler(s) and pigment(s) by weight of the coating composition.

Examples of additives are diluents, wetting agents, levelling agents anddispersants; defoaming agents such as silicone oils; stabilisers such asstabilisers against light and heat, e.g. hindered amine lightstabilisers (HALS); stabilisers against moisture (water scavengers) suchas substituted isocyanates, substituted silanes, ortho formic acidtrialkyl esters and synthetic zeolites; stabilisers against oxidationsuch as butylated hydroxyanisole and butylated hydroxytoluene;thickeners and anti-settling agents such as organo-modified clays(Bentone), polyamide waxes and polyethylene waxes.

Moreover, the base and/or the curing agent may be supplemented with oneor more solvents. Preferable examples of suitable solvents are organicsolvents such as toluene, xylene and naphtha solvent; ketones such asmethyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol andcyclohexanone; esters such as methoxypropyl acetate, n-butyl acetate and2-ethoxyethyl acetate; and mixtures thereof. However as regards theclaimed coating composition when for use in LEP, a solvent may not evenbe necessary due to the low viscosity of the remaining constituents ofthe coating composition because of the combined properties of thepolyetheraspartic esters and polyisocyanate curing agent. E.g the LEPcoating composition of the invention may be prepared in solvent-freeform and thus, provide a good environmental profile. Hence, in the LEPcoating composition preferably, the one or more solvents are included(or not included) in an amount of less than 25% by weight, such as lessthan 15% by weight, such as less than 10% by weight, preferably lessthan 5%, such as less than 2.5% by weight of the coating composition.Most preferably, when for use as an LEP coating composition, thecomposition is substantially free of any solvents meaning that one ormore organic solvents has not been explicitly added in order, forexample, to adapt the viscosity of the composition. “substantially freeof any solvents” means that, if at all, only small amounts of one ormore organic solvents are present in the coating composition as a resultof the use of for example typical coatings additives, which may beoptionally obtained commercially in solution in organic solvents.

When the claimed coating composition is for use as a topcoat, saidcomposition preferably contains one or more added solvents in additionto the solvents that might be comprised in the coating composition as aresult of the use of for example coating additives, which may beoptionally obtained commercially in solution in organic solvents.Preferably an added solvent is present in an amount in the range of10-30% by weight of the coating composition, such as in a range of15-25% such as about 20% of said coating composition.

The coating composition may be prepared by suitable techniques that arecommonly used within the field of coating production. The coatingcomposition may be prepared by mixing two or more components e.g. twopre-mixtures whereof one pre-mixture comprises the base composition andone pre-mixture comprises the curing agent. Prior to mixing one or bothof the pre-mixtures may be preconditioned to meet specific temperaturerequirements. It should be understood that when reference is made to thecoating composition, it is the mixed coating composition.

Mixing of the base composition (comprising the one or morepolyetheraspartic esters) and the curing agent (comprising the one ormore polyisocyanates) allows a chemical reaction between the aminogroups of the polyetheraspartic esters, and potential aliphaticpolyaspartic esters when present, and the isocyanate groups of thepolyisocyanates. The mixing ratio between the two components musttherefore be carefully controlled in order to obtain a coatingcomposition with the right physical properties. The mixing ratio isdefined as the volumetric or weight ratio between the base compositionand the curing agent. In the context of the present invention, thevolumetric mixing ratio between the base composition and the curingagent is typically between 1:5 and 5:1, such as between 1:4 and 4:1,such as between 1:3 and 3:1, preferably between 1:2 and 2:1, such asbetween 1:1.5 and 1.5:1, such as about 1:1.

Application of the Coating Compositions of the Invention

Application of the coating compositions can be done by standardapplication methods such as by brush or roller. Furthermore, the claimedcoating composition can be applied to the wind blade by sprayapplication such as for example by conventional air-atomized sprayapplication (topcoat) or by airless spray application (both topcoat andLEP). In practical embodiments, the base composition and the curingagent are mixed either in a single batch for normal spray application oras a continuous process when plural component spray equipment is used.

With the aim of facilitating easy application of the coating composition(e.g. by spray, brush or roller application techniques), the LEPcomposition typically has a viscosity in the range of 150-5000 mPa·s,such as 250 to 3000 mPa·s, preferably in the range of 500-2500 mPa·s,such as 500-2000 mPa·s; while the topcoat composition typically has aviscosity in the range of 50-500 mPa·s, such as about 50-300 mPa·s, suchas about 50-200 mPa·s. Typically, the LEP composition has a higherviscosity than the topcoat composition.

Preferably, the coating composition is applied in one or more layers andthe total dry film thickness of the coating composition is between 50and 1000 μm.

Also preferably, the part of the outer surface of the wind turbine bladecoated with the coating composition comprises at least a predominantportion of the leading edge of the blade, but the total surface of thewind turbine blade can be coated with the coating composition.

In the context of the invention, the wind blade to which the topcoatcoating composition is applied is typically pre-coated with one or morecoating layers comprising a primer to which the topcoat coatingcomposition is applied. Preferably, the wind blade to which the topcoatcoating composition is applied is pre-coated with at least one or morelayers of a primer.

In the context of the invention, the wind blade to which the LEP coatingcomposition is applied can be pre-coated with one or more coating layerscomprising a primer and/or a topcoat to which the coating composition isapplied. Preferably, the wind blade to which the LEP coating compositionis applied is pre-coated with at least one or more layers of a primerand/or a topcoat.

In one embodiment, the invention relates to a wind blade having on atleast a part of the outer surface thereof one or more coating layersprepared from a topcoat composition of the invention and thereon one ormore layers of an LEP coating prepared from an LEP coating compositionof the invention, wherein said LEP coating composition is applied to atleast a part of the leading edge of the wind blade. Optionally, the windblade has been be pre-coated with one or more coating layers comprisinga primer.

Hence, the present invention also provides a method for coating a windblade, said method comprising applying a coating composition as definedherein to at least a part of the surface of said wind blade; andallowing the coating composition to cure.

Since the use of the coating compositions of according to the inventionincludes both the use for topcoats and use in Leading Edge Protection, afurther embodiment of the invention provides a method for coating a windblade comprising the steps, i) applying a coating composition accordingto the invention for use as a topcoat to at least a portion of the windblade and allowing the composition to cure; followed by ii) applying acoating composition according to the invention for use in Leading EdgeProtection to at least the leading edge of a wind blade and allowing thecomposition to cure.

In another embodiment the invention provides a method for coating a windblade comprising the steps, i) applying a coating composition accordingto the invention for use in Leading Edge Protection to least the leadingedge of a wind blade and allowing the composition to cure, followed byii) applying a coating composition according to the invention for use asa topcoat to at least a portion of the wind blade and allowing thecomposition to cure.

Said wind blade may be pre-coated with a primer before applying thetopcoat and/or LEP coating composition.

After application of the coating composition to the wind blade, thecoating composition is allowed to cure under controlled ambienttemperature and humidity. The coating composition is preferably cured ata temperature not exceeding 70° C., in particular at a temperature inthe range of 0-45° C., such as a temperature in the range of 15-35° C.The actual temperature at which the coating composition can be cured isnormally set at the lower limit by the temperature at which the coatingcomposition is practically curable and at the upper limit by thetemperature at which the integrity of the wind blade and any underlyingcoats will be compromised.

The coating compositions of the present invention may also be used in amethod for repairing a wind blade. The method for repairing a wind bladewould comprise a step of applying the coating composition of the presentapplication to at least a portion of the wind blade. The coating can beapplied to substantially all of the wind blade, or just to a portion ofthe wind blade, such as the leading edge of the wind blade. In certainembodiments, one or more of the coating layers can be applied to atleast a portion of the wind blade. The wind blade repaired in thismanner can have a pre-existing coating or coating layers, some or all ofwhich may be removed prior to application of the claimed coatingcomposition. Alternatively, the claimed coating composition could bepainted over the existing coating layer(s). Thus, the invention alsorelates to a method for repairing and/or replacing or partly replacingan existing coating layer on a wind blade. In one embodiment, if thecoating composition is painted over an existing coating layer(s), anadhesion promoter may be applied on the existing coating layer beforeapplication of the coating composition of the invention, to improve theadherence of the coating composition. In another embodiment, no adhesionpromoter is applied. Adhesion promoters and uses thereof are known inthe art.

Preferred features of the claimed coating compositions (both topcoat andLEP compositions) are—in addition to a high degree offlexibility—cohesion of the film (as a result of the cross-linkingdensity), UV-resistance, gloss retention and adhesion to underlyingcoatings. Furthermore, preferably the coating composition, in particularthe LEP composition, provides a coating that provides good protectionagainst erosion caused by harsh weather conditions.

EMBODIMENTS OF THE INVENTION

In the following, embodiments of the invention are disclosed. The firstembodiment is denoted E1, the second embodiment is denoted E2 and soforth.

It should be understood that the various aspects, embodiments,implementations and features of the invention mentioned herein may beclaimed separately, or in any combination.

E1. Use of a coating composition comprising:

-   -   a) a base composition comprising a polyetheraspartic ester        having the formula (I) below

wherein each R represents a linear or branched C₁-C₁₀ alkyl residue,such as a linear or branched C₁-C₆ alkyl residue, preferably a methyl,ethyl, propyl or butyl residue; andwherein X is a polyether;and

-   -   b) a curing agent;        for coating of a wind turbine blade.        E2. The use according to embodiment 1, with the proviso that        said coating composition is not:        A coating composition comprising:    -   (a) an isocyanate-reactive component comprising:        -   (a1) at least one polyaspartic ester, and        -   (a2) optionally a polyetheraspartic ester;    -   (b) an isocyanate component comprising:        -   (b1) at least one isocyanate prepolymer, the isocyanate            prepolymer being a reaction product of components comprising            at least one aliphatic isocyanate and at least one polyether            polyol, the poly ether polyol having a weight-average            molecular weight of 400 to 6000 and the structure of formula            I:            HO—R¹ _(n)—R²  I,            wherein R¹ has one or more of the following structures:

-   -   R² is one or more of the following: hydrogen and an organic        group inert to an isocyanate group,    -   n is an integer of 6 to 100,    -   the amount of the —R¹ _(n)— structure is at least 40 wt % based        on the weight of the polyether polyol; and        -   (b2) at least one isocyanate oligomer containing not less            than two isocyanate groups,        -   the weight ratio of the isocyanate prepolymer (b1) to the            isocyanate oligomer (b2) being greater than 1:4 and less            than 4:1;    -   (c) a catalyst; and    -   (d) optionally an additive;        wherein the molar ratio of the isocyanate groups to the        isocyanate-reactive groups in the coating composition is from        1.5:1 to 4:1.        E3. The use according to any of embodiments 1-2, wherein X is a        polyether wherein the repeating unit contains an alkyl residue        of one or more carbon atoms linked by an oxygen atom, such as an        alkyl residue of between two to six carbon atoms linked by an        oxygen atom, such as an alkyl residue of two carbon atoms linked        by an oxygen atom;    -   wherein or more of said carbon atoms may be substituted with a        small alkyl such as for example methyl, ethyl or propyl.        E4. The use according to any of embodiments 1-3, wherein X has a        repeat unit of the structure below

-   -   wherein m is in the range of 2 to 35, such as in the range of 2        to 10, such as in the range of 2 to 6, such as in the range of 2        to 4.        E5. The use according to any of embodiments 1-4, wherein said        base composition comprises a blend of polyetheraspartic esters        having formula (I) comprising at least two polyetheraspartic        esters wherein X has a repeat unit of the structure below

wherein the blend is such that the average value of m is in the range of2 to 35, such as in the range of 2 to 10, such as in the range of 2 to6, such as in the range of 2 to 4, such as in the range of 2.5 to 3.E6. The use according to any of embodiments 1-5, wherein each R informula (I) represents an ethyl residue.E7. The use according to any of embodiments 1-4, wherein saidpolyetheraspartic ester is the reaction product of a dialkylmaleate,preferably a linear or branched C₁-C₁₀ dialkyl maleate, such as a linearor branched C₁-C₆ dialkyl maleate, such as diethyl maleate; and of apolyether polyamine according to the formula (II) below

wherein p is in the range of 2 to 35, such as in the range of 2 to 10,such as in the range of 2 to 6, such as in the range of 2 to 4.E8. The use according to any of embodiments 1-5, wherein said basecomposition comprises a blend of polyetheraspartic esters comprising atleast two polyetheraspartic esters which are each the reaction productof a dialkyl maleate preferably a linear or branched C₁-C₁₀ dialkylmaleate, such as a linear or branched C₁-C₆ dialkyl maleate, such asdiethyl maleate; and of at least two polyether polyamines according tothe formula (II) below

wherein the average value of p is in the range of 2 to 35, such as is inthe range of 2 to 10, such as in the range of 2 to 6, such as in therange of 2 to 4, such as in the range of 2.5 to 3.E9. The use according to any of embodiments 7-8, wherein saiddialkylmaleate is diethylmaleate.E10. The use according to any of embodiments 1-9, wherein said curingagent b) comprises one or more polyisocyanates.E11. The use according to any of embodiments 1-2, wherein said coatingcomposition comprises

-   -   a) a base composition comprising a polyetheraspartic ester        having the formula below

wherein X has a repeat unit of the structure below

wherein m is in the range of 2 to 35, such as in the range of 2 to 10,such as in the range of 2 to 6, such as in the range of 2 to 4;and

-   -   b) a curing agent comprising one or more polyisocyanates.        E12. The use according to any of embodiments 1 or 11, wherein        said coating composition comprises    -   a) a base composition comprising a polyetheraspartic ester blend        having the formula below

wherein X has a repeat unit of the structure below

wherein the blend is such that the average value of m is in the range of2 to 35, such as in the range of 2 to 10, such as in the range of 2 to6, such as in the range of 2 to 4 such as in the range of 2.5 to 3; and

-   -   b) a curing agent comprising one or more polyisocyanates.        E13. The use according to any of embodiments 10-12, wherein one        or more of said one or more polyisocyanates is based on        hexamethylenediisocyanate (HDI).        E14. The use according to any of embodiments 10-12, wherein one        or more of said one or more polyisocyanates is based on a trimer        of hexamethylenediisocyanate (HDI).        E15. The use according to any of embodiments 10-14, wherein said        one or more polyisocyanates contains less than 0.5% isocyanate        monomer, preferably less than 0.3% isocyanate monomer such as        less than 0.1% isocyanate monomer; according to DIN EN ISO 10        283.        E16. The use according to any of embodiments 10-15, wherein the        average functionality of said one or more polyisocyanates is in        the range of 2-4, such as in the range of 3-4 or 2-3, such as in        the range of 2-2.5.        E17. The use according to any of embodiments 10-16, wherein a)        and b) are present in said coating composition in an amount so        that the stoichiometric ratio of the number of isocyanate groups        in the curing agent component to the number of amine groups in        the base component is in the range of 80:100 to 160:100, such as        90:100 to 125:100, such as 95:100 to 120:100, preferably in the        range of 100:100 to 120:100, such as 100:100 to 110:100 or        105:100 to 110:100; such as about 100:100.        E18. The use according to any of embodiments 1-17, wherein said        coating composition further comprises    -   c) one or more further components selected from fillers,        pigments, solvents and additives.        E19. The use according to embodiment 18, wherein said one or        more further component comprises one or more components selected        from the group consisting of calcium carbonate, dolomite, talc,        mica, barium sulphate, kaolin, silica, titanium dioxide, red        iron oxide, yellow iron oxide, black iron oxide, carbon black,        phthalocyanine blue and phthalocyanine green.        E20. The use according to any of embodiments 18-19, wherein the        total amount of filler(s) and pigment(s) is between 5-30%, such        as between 10-25% by weight of the coating composition.        E21. The use according to any of embodiments 1-20, wherein said        coating composition has a viscosity in the range of 150-5000        mPa·s, such as 250 to 3000 mPa·s, preferably in the range of        500-2500 mPa·s, such as 500-2000 mPa·s, such as about 1500        mPa·s.        E22. The use according to any of embodiments 1-21, wherein said        coating composition is cured at a temperature below 90° C., such        as below 70° C., such as a temperature in the range of 0-45° C.,        such as in the range of 15-35° C.        E23. The use according to any of embodiments 1-22, wherein said        base composition a) comprises less than 20%, such as less than        15%, such as less than 10%, such as less than 5%, such as less        than 1% of any aliphatic polyaspartic esters by weight of said        base composition.        E24. The use according to any of embodiments 1-22, wherein said        base composition a) optionally further comprises one or more        aliphatic polyaspartic esters,        wherein the ratio of polyetheraspartic ester blend to aliphatic        polyaspartic esters is in the range of 70:30 to 99:1, preferably        in the range of 80:20 to 99:1, such as in the range of 85:15 to        99:1, most preferably in range of 90:10 to 99:1 such as 95:5 to        99:1.        E25. The use according to any of embodiments 1-22, wherein said        coating composition is substantially free of any aliphatic        polyaspartic esters.        E26. The use according to any of embodiments 1-22, wherein said        base composition a) optionally further comprises one or more        aliphatic polyaspartic esters,        wherein the ratio of polyetheraspartic ester blend to aliphatic        polyaspartic esters is in the range of 70:30 to 99:1, preferably        in the range of 80:20 to 99:1, such as in the range of 85:15 to        99:1, most preferably in range of 90:10 to 99:1 such as 95:5 to        99:1; or        wherein said coating composition is substantially free of any        aliphatic polyaspartic esters.        E27. The use according to any of embodiments 1-26, wherein said        coating composition comprises one or more solvents, wherein the        total amount of solvent constitutes less than 25% by weight,        such as less than 15% by weight, such as less than 10% by        weight, such as less than 5% by weight, such as less than 2.5%        by weight of the coating composition.        E28. The use according to any of embodiments 1-26, wherein said        coating composition is substantially free of any solvents.        E29. The use according to any of embodiments 10-28, wherein said        one or more polyisocyanates has an isocyanate content of 5-25%,        such as 5-20%, such as 5-15%, preferably 6-14%, such as 6-11% or        8-14% or 10-12%; or such as about 6% or about 7% or about 8% or        about 9% or about 10% or about 11%.        E30. The use according to any of embodiments 10-29, wherein said        one or more polyisocyanates each contains aliphatic polyester        groups.        E31. The use according to any of embodiments 1-19 and 29-30,        wherein the total amount of filler(s) and pigment(s) is between        20-40%, such as between 25-30% by weight of the coating        composition.        E32. The use according to any of embodiments 1-19 and 29-31        wherein said coating composition has a viscosity in the range of        50-1000 mPa·s, such as in the range of 50-500 mPa·s.        E33. The use according to any of embodiments 1-19 and 29-32,        wherein said coating composition is cured at a temperature below        50° C., such as below 30° C., such as a temperature in the range        of −10-30° C.        E34. The use according to any of embodiments 1-19 and 29-33,        wherein said base composition a) further comprises one or more        aliphatic polyaspartic esters,        wherein the ratio of polyetheraspartic ester blend to aliphatic        polyaspartic esters is in the range of 40:60 to 60:40, such as        in the range of 45:55 to 55:45, such as about 50:50.        E35. The use according to any of embodiments 1-19 and 29-34,        wherein said coating composition comprises one or more solvents,        wherein the total amount of solvent constitutes an amount in the        range of 10-30% by weight of the coating composition, such as in        a range of 15-25% such as about 20% by weight of said coating        composition.        E36. The use according to any of embodiments 1-19 and 29-35        wherein said curing agent further comprises a polyisocyanate as        defined in any of embodiments 13-16 and having an isocyanate        content of between 20-26 w/w %, such as between 15-30 w/w %,        such as between 22 to 24 w/w %, such as about 23 w/w %.        E37. The use according any of embodiments 1-30, wherein said        composition is for use as a leading edge protective coating of        said wind turbine blade.        E38. The use according to any of embodiments 1-30, wherein said        coating composition is applied to at least the leading edge of        said wind turbine blade.        E39. The use according to any of embodiments 1-30, wherein said        coating composition is applied to the leading edge of said wind        turbine blade.        E40. The use according any of embodiments 1-19 and 29-36;        wherein said coating is for use as a topcoat for said wind        turbine blade.        E41. A wind turbine blade having on at least a part of the outer        surface thereof, a coating prepared from a coating composition        as defined in any one of embodiments 1-36.        E42. The wind turbine blade according to embodiment 41 having on        at least at the leading edge of said wind turbine blade, a        coating prepared from a coating composition as defined in any        one of embodiments 1-36.        E43. The wind turbine blade according to any of embodiments        41-42 having on the leading edge of said wind turbine blade, a        coating prepared from a coating composition as defined in any        one of embodiments 1-30.        E44. The wind turbine blade according to any of embodiments        41-43, wherein said coating constitutes the outermost coating        layer.        E45. The wind turbine blade according to any of embodiments        43-44, wherein said coating is a leading edge protective        coating.        E46. The wind turbine blade according to any of embodiments        43-45, wherein said coating is a leading edge protective        coating, and        wherein said coating has been applied on top of a topcoat, or        wherein said coating has been applied underneath a topcoat        preferably on top of a primer layer.        E47. The wind turbine blade according to embodiment 41 having a        first coating layer which is a topcoat prepared from a coating        composition as defined in any one of embodiments 1-19 and 29-36;        and on top of said first coating layer having a second coating        which is a LEP coat prepared from a coating composition as        defined in any of embodiments 1-30 applied over the first        coating layer on at least a part of the outer surface of said        wind turbine blade such as on the Leading edge of said wind        turbine blade.        E48. The wind turbine blade according to embodiment 41 having a        first coating layer which is a LEP coating prepared from a        coating composition as defined in any one of embodiments 1-30        applied on at least a part of the surface of said wind turbine        blade such as on the Leading edge of said wind turbine blade;        and on top of said first coating layer having a second coating        which is a topcoat prepared from a coating composition as        defined in any of embodiments 1-19 and 29-36 applied over the        outer surface of said wind turbine blade and over the first        coating layer of said wind turbine blade.        E49. The wind turbine blade according to any of embodiments        41-44 wherein said wind turbine blade has a primer layer applied        underneath the topcoat and/or leading edge protective coating        layer.        E50. A kit of parts comprising    -   i) a container comprising a) a base composition comprising a        polyetheraspartic ester having the formula (I) below

-   -   -   wherein each R represents a linear or branched C₁-C₁₀ alkyl            residue, such as a linear or branched C₁-C₆ alkyl residue,            preferably a methyl, ethyl, propyl or butyl residue; and            wherein X is a polyether; and

    -   ii) a container comprising b) a curing agent.        E51. The kit according to embodiment 50, wherein X is a        polyether wherein the repeating unit contains an alkyl residue        of one or more carbon atoms linked by an oxygen atom, such as an        alkyl residue of between two to six carbon atoms linked by an        oxygen atom, such as an alkyl residue of two carbon atoms linked        by an oxygen atom;        wherein or more of said carbon atoms may be substituted with a        small alkyl such as for example methyl, ethyl or propyl.        E52. The kit according to any of embodiments 50-51, wherein X        has a repeat unit of the structure below

-   -   wherein m is in the range of 2 to 35, such as in the range of 2        to 10, such as in the range of 2 to 6, such as in the range of 2        to 4.        E53. The kit according to any of 50-52, wherein said base        composition comprises a blend of polyetheraspartic esters having        formula (I) comprising at least two polyetheraspartic esters        wherein X has a repeat unit of the structure below

wherein the blend is such that the average value of m is in the range of2 to 35, such as in the range of 2 to 10, such as in the range of 2 to6, such as in the range of 2 to 4, such as in the range of 2.5 to 3.E54. The kit according to any of embodiments 50-53, wherein each R informula (I) represents an ethyl residue.E55. The kit according to any of embodiments 50-54 wherein saidpolyetheraspartic ester is the reaction product of a dialkylmaleate,preferably a linear or branched C₁-C₆ dialkyl maleate, such as diethylmaleate; and of a polyether polyamine according to the formula (II)below

wherein p is in the range of 2 to 35, such as in the range of 2 to 10,such as in the range of 2 to 6, such as in the range of 2 to 4.

E56. The kit according to any of embodiments 50-54, wherein said basecomposition comprises a blend of polyetheraspartic esters comprising atleast two polyetheraspartic esters which are each the reaction productof a dialkylmaleate, preferably a linear or branched C₁-C₁₀ dialkylmaleate, such as a linear or branched C₁-C₆ dialkyl maleate, such asdiethyl maleate; and of at least two polyether polyamines according tothe formula (II) below

wherein the average value of p is in the range of 2 to 35, such as inthe range of 2 to 10, such as in the range of 2 to 6, such as in therange of 2 to 4, such as in the range of 2.5 to 3.E57. The kit or the coating composition according to any of embodiments55-56, wherein said dialkylmaleate is diethylmaleate.E58. The kit according to any of embodiments 50-57 wherein said curingagent comprises one or more polyisocyanates.E59. The kit according to embodiment 50, wherein said kit comprises

-   -   i) a container comprising a) a base composition comprising a        polyetheraspartic ester having the formula below

wherein X has a repeat unit of the structure below

wherein, when m is in the range of 2 to 35, such as in the range of 2 to10, such as in the range of 2 to 6, such as in the range of 2 to 4;and

-   -   ii) a container comprising b) a curing agent comprising one or        more polyisocyanates.        E60. The kit according to any of embodiments 50 or 59, wherein        said kit comprises    -   i) a container comprising a) a base composition comprising a        polyetheraspartic ester blend having the formula below

wherein X has a repeat unit of the structure below

wherein the blend is such that the average value of m is in the range of2 to 35, such as in the range of 2 to 10, such as in the range of 2 to6, such as in the range of 2 to 4 such as in the range of 2.5 to 3; and

-   -   ii) a container comprising b) a curing agent comprising one or        more polyisocyanates.        E61. The kit according to any of embodiments 58-60, wherein one        or more of said one or more polyisocyanates is based on        hexamethylenediisocyanate (HDI).        E62. The kit according to any of embodiments 58-61, wherein one        or more of said one or more polyisocyanates is based on a trimer        of hexamethylenediisocyanate (HDI).        E63. The kit according to any of embodiments 55-62, wherein said        one or more polyisocyanates contains less than 0.5% isocyanate        monomer, preferably less than 0.3% isocyanate monomer such as        less than 0.1% isocyanate monomer; according to DIN EN ISO 10        283.        E64. The kit according to any of embodiments 58-63, wherein the        average functionality of said one or more polyisocyanates is in        the range of 2-4, such as in the range of 3-4 or 2-3, such as in        the range of 2-2.5.        E65. The kit according to any of embodiments 58-64, wherein said        one or more polyisocyanates has an isocyanate content of 5-20%,        such as 5-15%, preferably 6-14%, such as 6-11% or 8-14% or        10-12%; or such as about 6% or about 7% or about 8% or about 9%        or about 10% or about 11%.        E66. The kit according to any of embodiments 58-65, wherein said        one or more polyisocyanates each contains aliphatic polyester        groups.        E67. The kit according to any of embodiments 50-67, wherein said        base composition a) in container i) optionally further comprises        one or more aliphatic polyaspartic esters,        wherein the ratio of polyetheraspartic ester blend to aliphatic        polyaspartic esters is in the range of 70:30 to 99:1, such as in        the range of 80:20 to 99:1, such as in the range of 85:15 to        99:1, most preferably in range of 90:10 to 99:1 such as 95:5 to        99:1, or        wherein said base composition a) in container i) is        substantially free of any polyaspartic esters        E68. The kit according to any of embodiments 50-66, wherein said        base composition in container i) comprises less than 20%, such        as less than 15%, such as less than 10%, such as less than 5%,        such as less than 1% of any aliphatic polyaspartic esters by        weight of said base composition.        E69. The kit according to any of embodiments 50-67, wherein said        base composition in container i) comprises less than 20%, such        as less than 15%, such as less than 10%, such as less than 5%,        such as less than 1% of any acrylate-containing compounds by        weight of said base composition.        E70. The kit according to any of embodiments 50-69, wherein said        base composition in container i) comprises less than 20%, such        as less than 15%, such as less than 10%, such as less than 5%,        such as less than 1% of any silane-containing compounds by        weight of the coating composition.        E71. The kit according to any of embodiments 50-70, wherein:    -   the total amount of solvent in said base composition in        container i) constitutes less than 25% by weight, such as less        than 15% by weight, such as less than 10% by weight, such as        less than 5% by weight, such as less than 2.5% by weight of said        base composition, or said base composition is substantially free        of any solvents;        and/or    -   the total amount of solvent in said curing agent in container i)        constitutes less than 25% by weight, such as less than 15% by        weight, such as less than 10% by weight, such as less than 5% by        weight, such as less than 2.5% by weight of said curing agent,        or said curing agent is substantially free of any solvents.        E72. The kit according to any of embodiments 50-66, wherein said        base composition in container i) further comprises one or more        aliphatic polyaspartic esters,        wherein the ratio of polyetheraspartic ester blend to aliphatic        polyaspartic esters is in the range of 40:60 to 60:40, such as        in the range of 45:55 to 55:45, such as about 50:50.        E73. The kit according to any of embodiments 50-72, wherein said        base composition a) in container i) and/or said curing agent b)        in container ii) further comprises one or more further        components selected from fillers, pigments, solvents and        additives.        E74. The kit according to embodiment 73, wherein said one or        more further component comprises one or more components selected        from the group consisting of calcium carbonate, dolomite, talc,        mica, barium sulphate, kaolin, silica, titanium dioxide, red        iron oxide, yellow iron oxide, black iron oxide, carbon black,        phthalocyanine blue and phthalocyanine green.        E75. The kit according to any of embodiments 50-74 further        comprising instructions for use of said base composition and        said curing agent.        E76. A method for coating a wind blade comprising a step of        applying a coating composition as defined in any one of        embodiments 1-36 to at least a portion of the wind blade, such        as to the leading edge of the wind blade.        E77. The method according to embodiment 76 wherein said wind        blade has been pre-coated with a primer layer before application        of the coating composition as defined in any of embodiments        1-36.        E78. A method for coating a wind blade comprising the steps,    -   i) applying a coating composition as defined in any one of        embodiments 1-19 and 29-36 to at least a portion of the wind        blade and allowing the composition to cure; followed by    -   ii) applying a coating composition as defined in any of        embodiments 1-30 to at least a portion of the wind blade such as        at least the leading edge of a wind blade and allowing the        composition to cure.        E79. A method for coating a wind blade comprising the steps,    -   i) applying a coating composition as defined in any of        embodiments 1-30 to at least a portion of the wind blade such as        at least the leading edge of a wind blade and allowing the        composition to cure.    -   ii) applying a coating composition as defined in any one of        embodiments 1-19 and 29-36 to at least a portion of the wind        blade and allowing the composition to cure.        E80. The method according to any of embodiments 78-79, wherein        said wind blade has been pre-coated with a primer layer before        step i).        E81. A method for repairing a wind blade comprising a step of        applying the coating composition as defined in any one of        embodiments 1-36 to at least a portion of the wind blade such as        to the leading edge of the wind blade.        E82. A method for repairing and/or replacing or partly replacing        an existing coating layer on a wind blade comprising a step of        applying the coating composition as defined in any one of        embodiments 1-36 to at least a portion of the wind blade such as        to the leading edge of the wind blade.        E83. The method according to any of embodiments 81-82, wherein        said wind blade has one or more pre-existing coating layers;        wherein said one or more existing coating layers are painted        over with said coating composition, or        wherein said one or more pre-existing coating layers, are at        least partly removed prior to application of said coating        composition, or        wherein said one or more pre-existing coating layers, are        completely removed prior to application of said coating        composition.        E84. The method according to any of embodiments 81-83, wherein        said wind blade has a pre-existing coating layer which is a        Leading Edge Protection coating layer;        wherein said leading edge protection coating layer is painted        over by said coating composition, or wherein said leading edge        protection coating layer is at least partly removed prior to        application of said coating composition, or        wherein said leading edge protection coating layer is completely        removed prior to application of said coating composition.        E85. The method according to any of embodiments 74-84, wherein        said coating composition is applied by brush or roller, or by        spray application, such as by airless spray application to said        wind blade.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference in theirentirety and to the same extent as if each reference were individuallyand specifically indicated to be incorporated by reference and were setforth in its entirety herein (to the maximum extent permitted by law),regardless of any separately provided incorporation of particulardocuments made elsewhere herein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention are to be construed to cover boththe singular and the plural, unless otherwise indicated herein orclearly contradicted by context. For example, the phrase “thecomposition” is to be understood as referring to various “compositions”of the invention or particular described aspect, unless otherwiseindicated.

The description herein of any aspect or aspect of the invention usingterms such as “comprising”, “having,” “including” or “containing” withreference to an element or elements is intended to provide support for asimilar aspect or aspect of the invention that “consists of”, “consistsessentially of” or “substantially comprises” that particular element orelements, unless otherwise stated or clearly contradicted by context(e.g., a composition described herein as comprising a particular elementshould be understood as also describing a composition consisting of thatelement, unless otherwise stated or clearly contradicted by context).

The use of any and all examples, or exemplary language (including “forinstance”, “for example”, “e.g.”, and “such as”) in the presentspecification is intended merely to better illuminate the invention, anddoes not pose a limitation on the scope of invention unless otherwiseindicated.

Headings and sub-headings are used herein for convenience only, andshould not be construed as limiting the invention in any way. The use ofany and all examples, or exemplary language (including “for instance”,“for example”, “e.g.”, and “such as”) in the present specification isintended merely to better illuminate the invention, and does not pose alimitation on the scope of invention unless otherwise indicated. Thecitation and incorporation of patent documents herein is done forconvenience only, and does not reflect any view of the validity,patentability and/or enforceability of such patent documents.

It should be understood that the various aspects, embodiments,implementations and features of the invention mentioned herein may beclaimed separately, or in any combination.

EXPERIMENTAL

The invention will be illustrated by the following non-limitingexamples.

Rain Erosion Test

The Rain Erosion Test (RET) is widely accepted as being the mostsuitable test for evaluating anti-erosive properties of coatings on theleading edge of wind turbine blades. The idea is to simulate the erosiveeffect from collision with raindrops, dust particles, hailstone and thelike by creating a controlled rain field in which the coated surfacemoves at high speed.

Rain Erosion Test (RET) was carried out using a rotating arms test rigwhich was designed for the purpose by R&D A/S. The test was carried outaccording to the DNVGL-RP-0171 Recommended Practice, Testing of RotorBlade Erosion Protection Systems.

The erosion damage was reproduced on specimens mounted on an arm whichrotates horizontally, through an artificial rain field. The rain impactsthe surface of the test specimen and erodes the surface, which isprotected with the coating to be tested. The degree of erosion damagecaused by the droplet impacts was inspected and documented. This wasperformed by visual inspection and picture documentation at definedintervals. Detailed picture documentation enables the investigation ofthe initial damage at the end of the incubation period, as well as thedamage progress. The time needed to erode the surface to a specifiedlimit, was the measure which is used to compare the performance of theprotections systems with each other. There are two erosion stages whichare commonly used to specify the survival time of the specimens:

-   -   1. End of incubation period: The incubation period is defined as        the exposure time until the first damage is visually detectable        on the outer surface of the test specimen. The incubation period        depends on the impact speed and thus, for rotating arm test        rigs, on the position on the specimen.    -   2. Breakthrough to the underlying substrate: Breakthrough is        defined as the point in time when the erosion breaks through the        protective layer to the underlying substrate. The time of        breakthrough depends on the impact velocity and thus, for        rotating arm test rigs it also depends on the location on the        specimen.

45 cm long U-shaped test specimens based on NACA 634-021 aerofoilgeometry simulating the leading edge of a wind turbine blade (asdescribed in Appendix A.1, DNVGL-RP-0171), consisting of a compositesubstrate were coated with 200-600 μm (dry film thickness) of thecoating compositions to be tested. The coating compositions were curedat controlled laboratory conditions, typically 25° C. and 50% RH, for atleast 7 days to secure complete cure of the binder system.

Three test specimens were then mounted on the horizontal rotor arms,with a radial position of 1 m for the center of the specimen. The rotorwas spun at a controlled radial velocity resulting in a range of testsubject velocities.

Tables 1a and 1b below indicate the test condition parameters specifiedand/or monitored during each test.

TABLE 1a Rain Erosion Test conditions for experiments in table 4a andtable 5 Test Parameter Unit Nominal condition Speed (tip-centre-root)m/s 155-130-105 Rain field mm/h 29-33    Water temperature ° C. 8 Waterquality μS <5 Test chamber temperature ° C. 8-10   Mean droplet size,diameter, d Mm 2.2

TABLE 1b Rain Erosion Test conditions for experiments in table 4b andtable 6 Test Parameter Unit Nominal condition Speed (tip-centre-root)m/s 140-115-95 Rain field mm/h 29-33  Water temperature ° C. 8 Waterquality μS <5 Test chamber temperature ° C. 8-10  Mean droplet size,diameter, d mm 2.2

General Procedure for Preparation of Coating Compositions

The components of each of the base composition a) and the curing agentb) were produced by mixing the indicated ingredients for each of a) andb) in a conventional manner known to the person skilled in the art.

Component a) was then subsequently mixed with Component b) prior toapplication.

The mixed coating composition was applied to the composite testspecimens, which were primed in advance, by brush application. TheExamples below illustrates six coating compositions within the scope ofthe invention and one comparative coating composition wherein polyetheraspartic ester has been substituted with an aliphatic aspartic ester.

The LEP coating compositions in table 4a and 5 were applied directly onthe primed test specimens while the LEP coating compositions in table 4bwere applied on primed test specimens coated with a topcoat.

Tables 2 and 3 below indicates the identity of aspartic ester andpolyisocyanates applied in the examples.

TABLE 2 Aspartic esters applied in the examples (available from CovestroDeutschland AG, Leverkusen, Germany). Amine value Aspartic esterDescription (mg KOH/g) Aliphatic polyaspartic ester Aminofunctionalco-reactant 199-203 1: Desmophen NH 1420 for polyisocyanates. Aliphaticpolyaspartic ester Aminofunctional co-reactant 202-208 2: Desmophen NH1423 for polyisocyanates. Polyetheraspartic ester: Aminofunctionalco-reactant 170-210 Desmophen NH 2850 XP for polyisocyanates.

TABLE 3 Polyisocyanates applied in the examples (available from CovestroDeutschland AG, Leverkusen, Germany). Isocyanate Functionality ViscosityComposition Polyisocyanate Description content (%) (n) (mPa*s) LEPPolyisocyanate 1: Polyester-modified 11.0 2.2 1350 Desmodur Epolyisocyanate 2863 XP prepolymer based on hexamethylene-1,6-diisocyanate (HDI) LEP Polyisocyanate 2: Aliphatic 11.0 3.8 6000Desmodur N polyisocyanate, 3800 flexibilizing HDI trimer. LEPPolyisocyanate 3: Aliphatic 20.0 2.5 500 Desmodur polyisocyanate XP 2860based on hexamethylene diisocyanate LEP Polyisocyanate 4: Aliphatic 6.04.0 2500 Desmodur prepolymer XP 2599 containing ether groups and basedon hexamethylene-1,6- diisocyanate (HDI) Topcoat Polyisocyanate 5:aliphatic 23.5 3.2 730 Desmodur polyisocyanate N 3900 resin based onhexamethylene diisocyanate

Tables 4 and 5 indicate compositions and RET results for coatingcompositions of the invention and for comparative coating compositionswith an aliphatic polyaspartic ester fully or partly substituting thepolyetheraspartic ester.

The amounts of each component indicated in the coating compositions inTables 4 and 5 are given in percentages by weight of each total coatingcomposition.

RET results are indicated in Table 4a as follows:

End of incubation period:

-   -   ≥30 min: *    -   ≥60 min: **    -   ≥120 min: ***        Breakthrough to the underlying substrate:    -   ≥30 min: +    -   ≥60 min: ++    -   ≥120 min: +++

TABLE 4a LEP coating compositions and RET results, comparative exampleComparative Model LEP LEP Coating Coating 1 composition ComponentAspartic ester: a) Aliphatic polyaspartic 33.8 ester 1 Polyetheraspartic ester 34.9 Additives: Wetting and 0.2 0.2 dispersing agentThixotropic additive 1.8 1.9 Defoamer 0.3 0.3 Light stabilizer 0.8 0.8Pigments and fillers: Pigments 5.1 5.3 Fillers 8.7 8.1 ComponentPolyisocyanate: b) Polyisocyanate 1 48.2 49.7 Stoichiometric ratio ofisocyanate 107:100 107:100 groups in b) to amine groups in a) Rain Endof ** * Erosion incubation Test period (RET) Breakthrough to the +++ ++underlying substrate

TABLE 4b LEP coating compositions and RET results, examples withincreasing amounts of aliphatic polyaspartic ester. Coating CoatingCoating Coating Coating Coating Component A B C D E F Component Asparticester: a) Aliphatic 0.0 6.3 12.5 18.7 24.9 31.0 polyaspartic ester 2polyether aspartic 31.7 24.4 18.2 12.1 6.0 0.0 ester Additives: Wettingand 0.1 0.1 0.1 0.1 0.1 0.1 dispersing agent Thixotropic 0.7 0.6 0.5 0.40.3 0.2 additive Defoamer 0.3 0.3 0.3 0.3 0.3 0.3 Levelling agent 1.01.0 1.0 1.0 1.0 1.0 Light stabiliser 0.6 0.6 0.6 0.6 0.6 0.6 Pigmentsand fillers: Pigments 9.1 9.0 9.0 9.0 9.0 8.9 Fillers 11.9 13.6 13.814.0 14.1 14.3 Component Polyisocyanate: b) Polyisocyanate 1 44.6 44.144.0 43.8 43.7 43.6 Stoichiometric ratio of isocyanate 111:100 109:100107:100 105:100 103:100 101:100 groups in b) to amine groups in a) RainErosion End of incubation ≥9 h ≥6 h ≥4 h ≥3 h ≥2 h ≥2 h Test (RET)period Breakthrough to ≥12 h  ≥7 h ≥6 h ≥6 h ≥6 h ≥4 h the underlyingsubstrate

TABLE 5 LEP coating compositions and RET results model coatings of theinvention. Model Model Model Model Model Coating 2 Coating 3 Coating 4Coating 5 Coating 6 Component Aspartic ester: a) Polyetheraspartic 32.430.5 32.8 41.4 23.8 ester Additives: Wetting and 0.6 — 0.6 0.8 0.5dispersing agent Thixotropic 2.2 2.2 2.2 2.8 1.6 additive Defoamer 0.50.3 0.5 0.6 0.4 Light stabiliser 0.6 — 0.6 0.8 0.5 Pigments and fillers:Pigments 5.1 10.6 5.1 6.5 3.7 Fillers 12.9 12.3 11.3 14.3 8.2 ComponentPolyisocyanates b) Polyisocyanate 1 45.7 44.1 Polyisocyanate 2 46.7Polyisocyanate 3 32.8 Polyisocyanate 4 61.4 Stoichiometric ratio ofisocyanate 109:100 109:100 110:100 109:100 109:100 groups in b) to aminegroups in a) Rain End of incubation *** *** ** * ** Erosion period Test(RET) Breakthrough to the underlying +++ +++ +++ + +++ substrateThe viscosities of the model LEP coating compositions lies in the rangeof 800-2500 mPa·s. while the comparative LEP coating has a viscosity ofabout 5500 mPa·s.

TABLE 6 Topcoat coating composition and RET results, model coatings ofthe invention. Component Component a) Aspartic ester: Aliphaticpolyaspartic 13.6 ester 1 Polyetheraspartic ester 13.3 Additives:Levelling agent 0.4 Light stabiliser 0.5 Thixotropic agent 2.5 Flattingagent 2.6 Wetting and 0.4 dispersing agent Solvents, pigments andfillers: Filler 16.5 Pigment 8.9 Solvent 23.0 Component b)Polyisocyanate Polyisocianate 5 18.4 Stoichiometric ratio of isocyanate107:100 groups in b) to amine groups in a) Rain Erosion End ofincubation period ≥2 h Test (RET) Breakthrough to the ≥3 h underlyingsubstrateThe formulation in Table 6 showed excellent properties for the use astopcoat in wind blades. The topcoat provide rain erosion protectiveeffect on its own even without leading edge protection. Furthermore, thetopcoat has very high abrasion resistance (60 mg, ASTM D4060, 23° C. and50% RH CS10, 1000 g, 1000 rotations), flexibility (<8 mmØ cylindricalmandrel test at 23° C. and 50% RH, ISO 1519), tensile strength (18%strain at break) and resistance to accelerated weathering tests (ΔE<1after 3000 hours, ISO 16474-3, type 1A (UVA-340), method 1).The topcoat composition has a viscosity in the range of 80-150 mPa·s.Characterization of various properties of the coating compositions canbe done for example by the following methods:Viscosity

The viscosity of the coating compositions was determined using Cone andPlate viscometer according to ISO 2884-1:1999 using a Cone and Plateviscometer set at a temperature of 25° C. and providing viscositymeasurement range of 0-5000 mPa·s.

Solids Content

The solids content in the coating compositions can be calculated inaccordance with ASTM D5201, or de by determination of the percentagevolume of non-volatile matter, dry film density and spreading rate ofcoating materials according to ISO 3233-1.

Calculation of the Volatile Organic Compound Content

The volatile organic compound (VOC) content of the coating compositionscan be calculated in accordance with ASTM D5201.

Bend Test

A procedure in accordance with ISO 6860 or ISO 1519 can be followed. A150-250 micron wet film is applied to a sanded and degreased steel panelof 0.8 mm thickness and, after curing, the coated metal panel is bentaround a cylindrical mandrel and the flexibility is assessed byobservation of cracking.

Impact

Impact can be tested according to ISO 6272-2, which specifies a methodfor evaluating the resistance of a dry film of paint, varnish or relatedproduct to cracking or peeling from a substrate when it is subjected toa deformation caused by a falling weight, dropped under standardconditions, acting on a small-area spherical indenter.

Taber Abrasion

Taber Abrasion is tested according to ASTM D 4060. A 1 kg weight isapplied to the coated steel panel. A CS-10 abrasive wheel was used and2×500 revolutions used. The results are presented in terms of the lossof film in mg.

Drying Time

Drying time can be evaluated using the Beck Koller method in accordancewith ISO 9117-4 which specifies a test for determining the times takento reach various stages of drying of organic coatings, using amechanical straight-line or circular drying-time recorder.

Artificial Weathering

The resistance of the coatings to UV degradation can be tested byartificial weathering according to ISO 16474-3, following the TestCycle 1. Test Cycle No 1: 4 hours UV-light at 60° C. with UVA-340 lamps(UVA-340, 0.83 W/m2 irradiation at 340 nm) followed by 4 hourscondensation at 50° C. for a total of 1000 to 3000 hours.

Glass Transition Temperature

The glass transition temperature (Tg) of the binder and or the coatingcomposition can be obtained by Differential Scanning calorimetry (DSC)measurements and/or by DMA Glass transition temperature (Tg) of thecured paint films determined by Dynamic Mechanical Analyser (DMA).

Tensile Strength

Tensile modulus and other aspects of the tensile stress/strainrelationship can be measured according to ISO 527.

The invention claimed is:
 1. A wind turbine blade comprising: an outersurface, and at least one coating applied to one part of the outersurface the at least one coating including a first coating prepared froma coating composition comprising: a) a base composition comprising apolyetheraspartic ester having formula (I) below

wherein each R represents a linear or branched C₁-C₁₀ alkyl residue; andwherein X is a polyether; and b) a curing agent.
 2. The wind turbineblade according to claim 1, wherein said base composition a) furthercomprises at least one aliphatic polyaspartic ester, and wherein a ratioof the polyetheraspartic ester to the at least one aliphaticpolyaspartic ester is in a range of 7:3 to 99:1.
 3. The wind turbineblade according to claim 1, wherein said base composition comprises lessthan 20% of any aliphatic polyaspartic esters by weight.
 4. The windturbine blade according to claim 1, wherein X is a polyether including arepeating unit containing an alkyl residue of 1 to 6 carbon atoms linkedby an oxygen atom.
 5. The wind turbine blade according to claim 4,wherein the alkyl residue of the repeating unit is a methyl, ethyl orpropyl residue.
 6. The wind turbine blade according to claim 1, whereinX is a polyether including a repeating unit as shown below

wherein m is in a range of 2 to
 35. 7. The wind turbine blade accordingto claim 6, wherein m is in a range of 2 to
 4. 8. The wind turbine bladeaccording to claim 1, wherein each R in formula (I) represents an ethylresidue.
 9. The wind turbine blade according to claim 1, wherein saidcuring agent comprises one or more polyisocyanates.
 10. The wind turbineblade according to claim 9, wherein said one or more polyisocyanatesincludes an isocyanate content of 5-20% by weight, and/or wherein anaverage functionality of said one or more polyisocyanates is in a rangeof 2 to
 4. 11. The wind turbine blade according to claim 9, wherein atleast one of said one or more polyisocyanates contains aliphaticpolyester groups.
 12. The wind turbine blade according to claim 9,wherein said one or more polyisocyanates includes an isocyanate contentof 10-12% by weight.
 13. The wind turbine blade according to claim 1,wherein a stoichiometric ratio of a number of isocyanate groups in thecuring agent to a number of amine groups in the base composition is in arange of 4:5 to 8:5.
 14. The wind turbine blade according to claim 1,wherein said coating composition further comprises: c) at least one of afiller, a pigment, a solvent, and an additive.
 15. The wind turbineblade according to claim 1, wherein the at least one part includes atleast a portion of a leading edge of the wind turbine blade, such thatsaid first coating is a leading edge protective coating.
 16. The windturbine blade according to claim 15, wherein said leading edgeprotective coating is applied on top of a topcoat.
 17. The wind turbineblade according to claim 15, wherein said leading edge protectivecoating is applied between a topcoat and a primer layer.
 18. The windturbine blade according to claim 1, wherein each linear or branchedC₁-C₁₀ alkyl residue is a methyl, ethyl, propyl, or butyl residue. 19.The wind turbine blade according to claim 1, wherein said coatingcomposition is free of any aliphatic polyaspartic esters.
 20. The windturbine blade according to claim 1, wherein said coating compositionfurther comprises at least one of calcium carbonate, dolomite, talc,mica, barium sulphate, kaolin, silica, titanium dioxide, red iron oxide,yellow iron oxide, black iron oxide, carbon black, phthalocyanine blueand phthalocyanine green.